Turbine Engine Operational Testing

ABSTRACT

Systems and methods for conditionally performing engine operational tests for a turbine engine are provided. A system comprising at least one processor can be configured to obtain sensor data associated with at least one sensor for a turbine engine. The sensor data identifies a current fuel flow associated with the turbine engine. The system can determine a predicted fuel flow of the turbine engine based at least in part on the current fuel flow and a fuel flow reduction associated with an engine operational test. The system can compare the predicted fuel flow to at least one threshold. The system can selectively initiate the engine operational test based on comparing the predicted fuel flow to the at least one threshold.

FIELD

The present disclosure relates generally to aerial vehicles.

BACKGROUND

An aerial vehicle can rely on one or more engines such as jet turbineengines, turbofan engines, and turbojet engines to control the aerialvehicle. An engine control system is provided that allows the pilot tocontrol the amount of power and/or thrust generated by the engine. Manymodern control systems, for example, may include an input lever thatcommunicates pilot input to one or more engine controllers. The enginecontrollers generate commands to regulate the amount of power generatedby the engine based on the pilot input. If the turbine engine does notrespond to the controller commands in an anticipated manner, a safetyissue may arise. Accordingly, many control systems attempt to detectthrust control malfunctions, and provide an automated response. Forexample, engine control systems may shut down or reduce engine thrust inresponse to a detected thrust control malfunction.

To ensure proper operation of thrust control malfunction responsefunctions, tests of these control systems are often performed.Traditionally, these tests are only performed if one or more enginebleeds are being executed for the turbine engine.

BRIEF DESCRIPTION

Aspects and advantages of the disclosed technology will be set forth inpart in the following description, or may be obvious from thedescription, or may be learned through practice of the disclosure.

According to example embodiments of the disclosed technology there isprovided a computer-implemented method of reducing combustor blowoutduring turbine engine testing. The method comprises receiving, by asystem comprising at least one processor, sensor data associated with atleast one sensor for a turbine engine. The sensor data identifies acurrent fuel flow associated with the turbine engine. The methodincludes determining, by the system, a predicted fuel flow of theturbine engine based at least in part on the current fuel flow and afuel flow reduction associated with an engine operational test,comparing, by the system, the predicted fuel flow to at least onethreshold, and selectively initiating, by the system, the engineoperational test. The engine operation test is selectively initiatedbased on comparing the predicted fuel flow to the at least onethreshold.

According to example embodiments of the disclosed technology there isprovided a system, comprising one or more sensors configured to generatesensor data including one or more engine parameters of a turbine engine,and one or more processors. The one or more processors are configured todetermine a current fuel flow of the turbine engine, determine apredicted fuel flow of the turbine engine based on activation of a flowreduction valve of a fuel control system associated with the turbineengine, verify whether the predicted fuel flow satisfies at least onecriteria associated with lean blowout of a combustor of the turbineengine, and activate the reduction valve of the fuel control system inresponse to the predicted fuel flow satisfying the at least onecriteria.

According to example embodiments of the disclosed technology there isprovided a non-transitory computer-readable medium storing computerinstructions, that when executed by one or more processors, cause theone or more processors to perform operations. The operations comprisedetermining a current fuel flow rate associated with a turbine engine,inputting the current fuel flow rate into one or more models todetermine a predicted fuel flow rate of the turbine engine, determiningif the predicted fuel flow rate satisfies at least one thresholdcriterion associated with a control malfunction system of the turbineengine, and testing the control malfunction system if the predicted fuelflow rate satisfies the threshold criterion.

These and other features, aspects and advantages of the disclosedtechnology will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the disclosed technology and, together with thedescription, serve to explain the principles of the disclosedtechnology.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present disclosure, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 depicts a block diagram of an example of an aerial vehicle inwhich embodiments of the present disclosure may be practiced;

FIG. 2 depicts a block diagram of an example engine control system inaccordance with example embodiments of the present disclosure;

FIG. 3 depicts a block diagram of a thrust control managementaccommodation test unit in accordance with example embodiments of thepresent disclosure;

FIG. 4 is a graphical representation of a minimum fuel flow thresholdfor performing a thrust control management accommodation test inaccordance with example embodiments of the present disclosure;

FIG. 5 is a flowchart describing a process of selectively activating athrust control management accommodation test in accordance with exampleembodiments of the present disclosure; and

FIG. 6 depicts a block diagram of an example of a computing system.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the disclosure,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation, not limitation of thedisclosed embodiments. In fact, it will be apparent to those skilled inthe art that various modifications and variations can be made in thepresent disclosure without departing from the scope or spirit of theclaims. For instance, features illustrated or described as part ofexample embodiments can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present disclosurecovers such modifications and variations as come within the scope of theappended claims and their equivalents.

As used in the specification and the appended claims, the singular forms“a,” “an,” and “the” include plural referents unless the context clearlydictates otherwise. The use of the term “about” in conjunction with anumerical value refers to within 25% of the stated amount.

Example aspects of the present disclosure are directed systems andmethods for avoiding combustor blowout in gas turbine engines, and moreparticularly, to systems and methods for selectively performing engineoperational tests based on predicted fuel flow to the gas turbineengine. According to example embodiments, a test system is provided thatreceives sensor data from one or more sensors associated with the jetturbine engine. The test system determines a current fuel flowassociated with the jet turbine engine from the sensor data. The testsystem uses the current fuel flow to determine a predicted fuel flow ofthe turbine engine if a engine operational test is activated for theturbine engine. The test system compares the predicted fuel flow withone or more thresholds such as a minimum fuel flow to avoid lean blowout(LBO) of the combustor section of the jet turbine engine. If thepredicted fuel flow satisfies the threshold, such as by meeting theminimum fuel flow requirement, the test system activates the engineoperational test of the turbine engine. If the predicted fuel flow doesnot satisfy the threshold, such as by being below the minimum fuel flowrequirement, the system can skip the engine operational test in aneffort to avoid lean blowout. The test system can additionally generatean identifier that the engine operational test was skipped in someimplementations.

According to example embodiments, the test system performs the predictedfuel flow analysis prior to initiating an engine operational test thatresults in a reduced fuel flow to the turbine engine. For example, thetest system may determine whether the predicted fuel flow satisfies athreshold prior to testing a thrust control response system of an aerialvehicle. The thrust control response system may respond to malfunctionsof the thrust control system by reducing engine thrust. Moreparticularly, the test system may determine whether the predicted fuelflow satisfies a threshold prior to initiating a test of a cutbackfunction associated with a thrust control malfunction accommodation(TCMA) system of the turbine engine. The TCMA cutback function mayprovide a reduced fuel flow to the jet turbine engine in response to aTCMA command. For example the TCMA system may include a flow reductiondevice such as a flow reduction valve to reduce fuel flow to the turbineengine over a range of input commands. The range of input commands mayresult in different fuel metering valve positions to regulate enginethrust. The flow reduction valve may reduce fuel flow over the range offuel metering valve positions. Accordingly, the test system maydetermine whether the predicted fuel flow during a test of the flowreduction valve is at or above a minimum fuel flow to provide a leanblowout margin.

According to example embodiments of the disclosed technology, the testsystem is configured to determine a current fuel flow associated withthe jet turbine engine prior to initiating an engine operational test.For example, the test system can be configured to receive sensor datarepresenting a current fuel flow associated with the turbine engine. Forexample, the current fuel flow may be a current fuel flow raterepresented by one or more engine parameters of the sensor data. Thetest system may receive the sensor data directly from the one or moresensors, or may receive the sensor data from a memory or other storagelocation. In some examples, the test system can be configured todetermine a current fuel flow associated with the turbine engine usingthe sensor data or through other techniques. For example, the system mayderive a current fuel flow from one or more other engine parameters.

According to some implementations of the disclosed technology, the testsystem can be configured to receive sensor data identifying one or moreadditional engine parameters. The test system can predict a fuel flowduring the maintenance test based on these one or more additional engineparameters in addition to or in place of the current fuel flow. Forexample, the test system may be configured to determine a predicted fuelflow based on one or more of a fuel split ratio to fuel nozzles, a fueltemperature, an engine core speed, and a high pressure compressordischarge pressure.

In accordance with some embodiments, the test system is configured toutilize one or more engine and/or fuel flow models to determine apredicted fuel flow rate. For example, the test system can input acurrent fuel flow rate to the one or more models, and receive as anoutput a predicted fuel flow rate. In other examples, the test systemcan input the current fuel flow rate and one or more additional engineparameters to the one or more models and receive a predicted fuel flowrate.

In accordance with example embodiments, the test system is configured tocompare the predicted fuel flow rate with one or more thresholds inorder to avoid lean blowout of the combustor section of the turbineengine. In some examples, the threshold is a minimum fuel flow tomaintain a lean blowout margin. In some embodiments, the threshold isvariable based on engine operating conditions or a current engine state.For example, the minimum fuel flow rate may change based on engineoperating parameters. In other examples, a constant threshold can beused.

Embodiments of the disclosed technology provide a number of technicalbenefits and advantages, particularly in the area of turbine engineoperation. As one example, the disclosed technology provides for morestable turbine engine performance by ensuring that future operatingconditions will not cause an undesirable engine state. The disclosedtechnology can predict a fuel flow to the engine prior to performing ascheduled engine operation test, such as a test of the thrust controlmalfunction system utilized with many aircraft. By determining whetherthe predicted fuel flow satisfies minimum fuel flow rates during thescheduled operation, the system can avoid initiating an operation thatwill cause an undesirable engine state such as lean blowout of thecombustor.

Embodiments of the disclosed technology additionally provide a number oftechnical benefits and advantages in the area of computing technology.For example, the disclosed system can obtain sensor data identifyingmeasured engine parameters of a turbine engine and automaticallydetermine whether performance of an engine operational test will causean undesirable engine state. A computing system implemented inaccordance with the disclosed technology can determine a predictedengine state, such as a predicted fuel flow based on measured engineparameters. In this manner, the computing system can more accurately andefficiently determine an engine state to avoid performing a maintenanceoperation that can cause an undesirable engine state. By way of example,a computing system can determine a predicted fuel flow rate to moreaccurately predict whether sufficient lean blowout margin exists, whencompared with traditional techniques that may look at indirect factors.For example, by predicting a fuel flow rate a more accuraterepresentation of the lean blowout margin can be provided, when comparedwith techniques that may look at indirect factors such as whether bleedis being performed.

FIG. 1 depicts a block diagram of an example aerial vehicle 10 accordingto example embodiments of the present disclosure. The aerial vehicle 10can include one or more engines 12 that can cause operations, such aspropulsion of and/or onboard power generation for the aerial vehicle 10.An engine 12 can be a gas turbine engine such as a jet turbine engine,turboprop engine, turbofan engine, a turbo shaft engine, or any othersuitable engine.

The aerial vehicle 10 can include an onboard computing system includingone or more onboard computing devices that can be associated with, forexample, an avionics system. The one or more onboard computing devicescan be coupled to a variety of systems on the aerial vehicle 10 over oneor more communication networks including for example or more data busesand/or combinations of wired and/or wireless communication links. Inexample embodiments, the avionics system may include a flight managementsystem (FMS) 20 and vehicle control system (VCS) 16 as shown in FIG. 1.It will be appreciated that an FMS 20 and VCS 16 are broadly depicted byway of example only in FIG. 1 to represent the many varied controlsystems that may be implemented by onboard computing devices of theaerial vehicle.

The onboard computing device(s) may provide or implement the flightmanagement system 20. In example embodiments, the flight managementsystem can automate the tasks of piloting and tracking the flight planof the aerial vehicle 10. It should be appreciated that the flightmanagement system can include or be associated with any suitable numberof individual microprocessors, power supplies, storage devices,interface cards, auto flight systems, flight management computers, andother standard components. The flight management system can include orcooperate with any number of software programs (e.g., flight managementprograms) or instructions designed to carry out the various methods,process tasks, calculations, and control/display functions necessary foroperation of the aerial vehicle 10.

The onboard computing device(s) can also provide or implement one ormore aerial vehicle control system(s) 16. The aerial vehicle controlsystem(s) 16 can be configured to perform various aerial vehicleoperations and control various settings and parameters associated withthe aerial vehicle 10. For instance, the aerial vehicle controlsystem(s) 16 can be associated with the one or more engine(s) 12 and/orother components of the aerial vehicle 10. The aerial vehicle controlsystem(s) 16 can include, for instance, digital control systems,throttle systems, inertial reference systems, flight instrument systems,engine control systems, auxiliary power systems, fuel monitoringsystems, engine vibration monitoring systems, communications systems,flap control systems, flight data acquisition systems, a flightmanagement system, a landing system, and other systems.

In some implementations, the vehicle control system 16 includes one ormore engine controllers. For example, vehicle control system 16 mayinclude an electronic engine controller (EEC) for each engine 12 in someembodiments. In other examples, vehicle control system 16 may include aFull Authority Digital Engine Control (FADEC) system. A FADEC system isoften used for aerial vehicles having two or more engines because theFADEC system dynamically controls the operation of each gas turbineengine and requires minimal, if any, supervision from the pilot. Thevehicle control system may include other control systems such as a fuelcontrol system including one or more fuel controllers configured tocontrol fuel flow for the one or more engines 12.

The aerial vehicle 10 can additionally include one or more sensors 14.The one or more sensors 14 can be used to detect one or more parametersrelated to the engine(s) 12, aerial vehicle 10, and/or atmosphereexternal to the aerial vehicle. The one or more sensors 14 cancommunicate the one or more detected parameters to the flight managementsystem (FMS) 20 and/or vehicle control system (VCS) 16. In someimplementations, the one or more sensors and/or FMS 20 and/or VCS 16 cancommunicate parameters to one or more external components.

In example embodiments, the onboard computing device(s) can be incommunication with a display system, such as the flight displays in acockpit of the aerial vehicle 10. More specifically, the display systemcan include one or more display device(s) configured to display orotherwise provide information generated or received by the onboardcomputing system. In example embodiments, information generated orreceived by the onboard computing system can be displayed on the one ormore display device(s) for viewing by flight crew members of the aerialvehicle 10. The display system can include a primary flight display, amultipurpose control display unit, or other suitable flight displayscommonly included within the cockpit of the aerial vehicle 10.

The vehicle control system 16 and flight management system 20 maygenerally include one or more processor(s) and associated memoryconfigured to perform a variety of computer-implemented functions, suchas various methods, steps, calculations and the like disclosed herein.In some examples, control systems such as an engine control systemand/or fuel control system may be programmable logic devices, such as aField Programmable Gate Array (FPGA), however they may be implementedusing any suitable hardware and/or software.

The term processor may generally refer to integrated circuits, and mayalso refer to a controller, microcontroller, a microcomputer, aprogrammable logic controller (PLC), an application specific integratedcircuit (ASIC), a Field Programmable Gate Array (FPGA), and otherprogrammable circuits. Additionally, the memory described herein maygenerally include memory element(s) including, but not limited to,computer readable medium (e.g., random access memory (RAM)), computerreadable non-volatile medium (e.g., flash memory), a compact disc-readonly memory (CD-ROM), a magneto-optical disk (MOD), a digital versatiledisc (DVD) and/or other suitable memory elements or combinationsthereof.

Any one or a combination of the flight management system and vehiclecontrol system may also include a communications interface. Thecommunications interface can include associated electronic circuitrythat is used to send and receive data. More specifically, thecommunications interface can be used to send and receive data betweenany of the various control systems. Similarly, a communicationsinterface at any one of the controllers may be used to communicate withoutside components such as another aerial vehicle and/or ground control.A communications interface may be any combination of suitable wired orwireless communications interfaces.

The numbers, locations, and/or orientations of the components of exampleaerial vehicle 10 are for purposes of illustration and discussion andare not intended to be limiting. Those of ordinary skill in the art,using the disclosures provided herein, shall understand that thenumbers, locations, and/or orientations of the components of the aerialvehicle 10 can be adjusted without deviating from the scope of thepresent disclosure.

A gas turbine engine can include a fan and a core arranged in flowcommunication with one another. Additionally, the core of the gasturbine engine generally includes, in serial flow order, a compressorsection, a combustion section, a turbine section, and an exhaustsection. In operation, air is provided from the fan to an inlet of thecompressor section where one or more axial compressors progressivelycompress the air until it reaches the combustion section. Fuel is mixedwith the compressed air and burned within the combustion section toprovide combustion gases. The combustion gases are routed from thecombustion section to the turbine section. The flow of combustion gasesthrough the turbine section drives the turbine section and is thenrouted through the exhaust section, e.g., to atmosphere. In atraditional jet engine, the exhaust gases typically provide all of thethrust for the engine. In a turboprop engine, the exhaust gases drivethe turbine section, which generates power that is mechanicallytransmitted to a propeller which provides the majority of thrust for theengine. In a turbofan engine, some of the combustion air bypasses theturbine and drives a ducted fan which together with the exhaust gases ofthe turbine section generate thrust.

Vehicle control system 16 may execute operations to regulate fuel flowto the combustor of a turbine engine. For example, an engine controllermay include a thrust control system including a throttle input devicethat is provided to receive pilot input defining a desired thrust level.For example, the throttle input device may be movable between a maximumpower setting, and an idle or maximum reverse setting for the turbineengine. The pilot inputs are communicated to the engine controller whichgenerates commands to control the engine, such as by regulating the fuelflow. For example, the commands from the vehicle control system maycause actuators on the gas turbine to, for example, adjust one or morevalves between the fuel supply and combustors that regulate the flow andtype of fuel. The commands may also cause actuators to adjust inletguide vanes on the compressor and other control settings on the gasturbine.

A thrust control malfunction may exist when the turbine engine fails torespond appropriately to commands from the engine control system. Manyvehicle control systems provide a function to accommodate malfunctionsor other errors associated with the engine control system. For example,some engine control systems may shut down a turbine engine in responseto a detected malfunction. In other examples, a vehicle control systemmay cutback thrust generated by the turbine engine in response to adetected malfunction. For example, some vehicle control systems mayregulate or decrease the amount of fuel flow to the turbine engine inresponse to a detected malfunction.

FIG. 2 is a block diagram depicting an example vehicle control system 16that includes thrust control management. More particularly, the vehiclecontrol system 16 includes an engine control system 110 and a fuelcontrol system 120 for controlling operation of engine 12. Enginecontrol system 110 includes a thrust control system 112 and amalfunction detection unit 114. Thrust control system 112 may includeany number and type of input devices configured to receive pilot inputand to generate a corresponding output representing a desired thrustlevel. By way of example, the output of thrust control system 112 may beprovided to fuel control system 120 to regulate a fuel flow 130 betweena fuel tank 104 and engine 12. More particularly, fuel control system120 can include a fuel metering valve (FMV) 126 that can respond tocommands from engine control system 110 to regulate the fuel flowbetween fuel tank 104 and engine 12. It will be appreciated that maysystems and techniques for adjusting the fuel flow to a turbine enginemay be used in accordance with the present disclosure.

Malfunction detection unit 114 is configured to detect any malfunctionor error associated with the thrust control system 112. Although shownas part of the engine control system 110, malfunction detection unit 114may be incorporated within thrust control management accommodation(TCMA) system 122 in various embodiments. In response to a detectedmalfunction, malfunction detection unit 114 can issue a TCMA command 116to TCMA system 122. In response to the TCMA command 116, TCMA system 122can reduce fuel flow to engine 12. Various mechanisms may be providedfor reducing the fuel flow to an engine in response to a TCMA command.In one example, the TCMA system 122 includes a flow reduction valve(FRV) 124 configured to reduce the fuel flow 130 to engine 12. Flowreduction valve 124 may be actuated in response to TCMA command 116 toreduce the amount of fuel flow 130. Although shown separate from fuelflow 130, it will be appreciated that FRV 124 may be provided in thefuel flow path before or after FMV 126 in various embodiments. In otherexamples, FRV 124 may be a pressure-regulating valve configured toindirectly alter the flow of fuel between fuel tank 104 and engine 12.In some implementations, FRV 124 can be a servo valve or a control servovalve. It will be appreciated that many systems and techniques forreducing the fuel flow to a turbine engine may be used in accordancewith the present disclosure.

In order to ensure safe operation of an aerial vehicle 10, TCMA system122 may be periodically tested. For example, many commercial airlinersmay test the functionality of a TCMA system 122 after a predeterminednumber of flight cycles, which may be equal to one or more. Testing theTCMA system 122 may include actuating flow reduction valve FRV 124 oranother flow reduction device provided as part of the TCMA system 122.Actuating the flow reduction valve 124 may result in a reduced fuel flow130 to the engine 12. The reduced fuel flow that results from testingthe TCMA system may cause unintentional blowout of the turbine engine.

During normal operation of the turbine engine, the flame temperature andfuel mix are regulated in order to control the production of oxides ofnitrogen (in NOx) during the combustion process. For example, fuel andair can be premixed into a uniform mixture that may avoid creating areasof high combustion temperature. Additionally, the engine may be operatedbelow certain temperatures to avoid high levels of NOx production. Inthis manner, vehicle control system 16 can maintain NOx and carbonmonoxide (CO) emissions within predefined limits, and can maintain thecombustor firing temperature within predefined temperature limits.Example parameters that may be used include, but are not limited to,current compressor pressure ratio, compressor discharge temperature,ambient specific humidity, inlet pressure loss, and turbine exhaust backpressure.

A margin is typically provided in combustion systems such thatunder-fire events will not have a significant negative effect on engineperformance. In some modern engines, however, the margin can be small(or tight) such that under-fire may result in combustion dynamics or aloss of flame. Some gas turbines may operate at very lean fuel/air (F/A)ratios that are close to a lean blowout (LBO) boundary in order tomaintain low NOx emissions. If the fuel/air ratio is leaner than acorresponding LBO boundary, blowout of the engine flame in the combustormay occur. A blowout may occur in one or more cans of the combustor.Lean blowout, or weak extinction, may refer to the point at which afuel/air mixture is no longer flammable. For some systems, weakextinction may refer to the point at which there is a significant dropin the combustion efficiency and/or complete extinction of the flame.

Some aerial vehicles have included conditional test mechanisms that onlyperform a test of the TCMA system based on engine bleed criteria. Forexample, some techniques attempt to determine that a sufficient fuelflow is present by determining whether an environmental control system(ECS) bleed is being performed. An ECS bleed can be expected to increasethe fuel flow to the engine. As such, some techniques have verified thata bleed is being performed in order to ensure that a minimum fuel flowis present. If the engine bleed is currently being performed, such as bydrawing bleed air for the environmental control system, the test may beperformed. If the engine bleed is not currently being performed the TCMAtest may be skipped.

Techniques that rely on engine bleed criteria may be inefficient assuitable conditions can exist for performing an engine operational testeven when a bleed is not being performed. For example, it is possiblethat sufficient fuel flow may be present even without engine bleed beingperformed. A generator load or other factor may result in engine flowsufficient to conduct a TCMA test. Using an engine bleed or otherapproximation technique may lead to skipping a TCMA test when in factthe test can be performed while maintaining sufficient fuel flow to theturbine engine to avoid blowout.

In accordance with embodiments of the disclosed technology, a TCMA testcan be performed conditionally on the basis of the predicted fuel flowof the turbine engine during the test. For example, a TCMA test unit canbe provided as part of flight management system 20 and/or vehiclecontrol system 16. The TCMA test unit can be configured to conditionallyperform a TCMA test based on a predicted engine fuel flow.

FIG. 3 is a block diagram depicting a computing system 300 of aerialvehicle 10 in accordance with one embodiment of the disclosedtechnology. Computing system 300 includes a TCMA test unit 320, whichmay be implemented using one or more computing devices including one ormore processors and memory coupled to the one or more processors. In oneembodiment, TCMA test unit 320 is provided as part of flight managementsystem 20. In another embodiment. TCMA test unit 320 is provided as partof vehicle control system 16.

Sensor data 304 is received by TCMA test unit 320. Sensor data 304 mayinclude one or more engine parameters including at least one engineparameter identifying a fuel flow associated with engine 12. As anotherexample, the fuel flow may be derived from the sensor data, such as bydetermining a fuel flow rate from one or more other engine parametersreceived in the sensor data. The fuel flow may be represented by a fuelflow rate in one example, although any identification of the fuel flowmay be used. Sensor data may be received directly by TCMA test unit 320from sensors 14, or it may be received from a database or other datastorage device. In FIG. 3, sensor data 304 is received at a flowestimation unit 322.

Flow estimation unit 322 additionally receives a fuel flow model 342from model data store 340. Model data store 340 may store one or moreengine and or fuel flow models associated with engine 12. Model datastore 340 can store data including fuel flow model 342 in a format thatcan be accessed by the one or more processors. Fuel flow model 342 caninclude one or more table(s), function(s), algorithm(s), model(s),equation(s), etc. according to example embodiments of the presentdisclosure. Model data stores 340 may include any suitable data storagetechnology such as databases, files, data structures and the likeconfigured to store the associated information. In some embodiments, thedata store may comprise any combination of one or more of a hard diskdrive, RAM (random access memory), ROM (read only memory), flash memory,etc. In some embodiments, the aerial vehicle 10 may include a computermodel data store 340 that may provide information to the TCMA test unit320 and may also store results from the TCMA test unit 320, such as atest skip identifier 354.

The engine and fuel flow models may indicate various parametersassociated with the engine at different operating conditions. Forexample the one or more models may indicate an expected fuel flow rateof the turbine engine based on the set of operating conditions. Flowestimation unit 322 can access one or more fuel flow models 342. Inexample embodiments, flow estimation unit 322 can input the current fuelflow from sensor data 304 into the one or more fuel flow models 342.Flow estimation unit 322 can receive from the fuel flow model(s) one ormore predicted fuel flow rates based on performing a TCMA test.

For example, fuel flow model 342 may be configured to provide apredicted fuel flow rate based on a current fuel flow rate and a TCMAtest condition. The TCMA test condition can correspond to or represent aTCMA test being performed at the current fuel flow rate. Flow estimationunit 322 may receive the predicted fuel flow rate and provide apredicted fuel flow 324 to a comparison unit 326.

In example embodiments, comparison unit 326 can be configured to comparethe predicted fuel flow 324 with one or more thresholds. In one example,the one or more thresholds include a minimum fuel flow rate. The minimumfuel flow rate may be constant or variable rate in various embodiments.Comparison unit 326 compares the predicted fuel flow 324 with theminimum fuel flow to determine whether the predicted fuel flow is at orabove the minimum fuel flow rate. Comparison unit 326 can determinewhether the predicted fuel flow 324 satisfies a threshold criterionassociated with a TCMA test.

Comparison unit 326 provides a result of the comparison to thedetermination unit 328. For example, comparison unit 326 may provide anindication as to whether the predicted fuel flow rate satisfies thethreshold. Determination unit 328 can be configured to generate one ormore commands and/or identifiers based on the result provided bycomparison unit 326. For example, if the predicted fuel flow rate isabove the one or more thresholds, determination unit 328 may generate aTCMA test command 352. Determination unit 328 can provide the TCMA testcommand 352 to TCMA system 122. In response to the TCMA test command,the TCMA system can activate the TCMA test. If the predicted fuel flowrate does not satisfy the one or more thresholds, determination unit 328can generate a test skip identifier 354 indicating that the TCMA testwas skipped. In example embodiments, determination unit 328 may providethe test skip identifier 354 to flight management system 20. In oneexample, the test skip identifier is a flag, however, any suitableindication that a TCMA test was skipped can be used. The identifier canbe stored by the flight management system (FMS) 20 in order to track anumber of times the TCMA test was skipped. In one example, the flightmanagement system 20 may initiate a maintenance operation afterpredetermined number of TCMA tests are skipped.

TCMA test unit 320, including flow estimation unit 322, comparison unit326, and/or determination unit 328, may be implemented as hardware,software, or as a combination of hardware and software. The software maybe stored as processor readable code and implemented in a processor, asprocessor readable code for programming a processor for example. In someimplementations, one or more of the components can be implementedindividually or in combination with one or more other components as apackaged functional hardware unit (e.g., one or more electricalcircuits) designed for use with other units, a portion of program code(e.g., software or firmware) executable by a processor that usuallyperforms a particular function of related functions, or a self-containedhardware or software component that interfaces with a larger system, forexample. Each unit, for example, may include an application specificintegrated circuit (ASIC), a Field Programmable Gate Array (FPGA), acircuit, a digital logic circuit, an analog circuit, a combination ofdiscrete circuits, gates, or any other type of hardware or combinationthereof. Alternatively or in addition, these components may includesoftware stored in a processor readable device (e.g., memory) to programa processor for flight management system 20 and/or 16 to perform thefunctions described herein. The architecture depicted in FIG. 3 is oneexample implementation. These various computing-based elements may beconfigured at a single computing device, or may be distributed acrossmultiple computing devices.

Although FIG. 3 describes a TCMA test unit incorporated within theaerial vehicle, this is not required. For example, a TCMA test unit maybe implemented externally to an aerial vehicle. In some implementations,a ground-based control system can implement the TCMA test unit. Sensordata can be communicated in the aerial vehicle to the external TCMA testunit. The external TCMA test unit can determine whether the test shouldbe performed and provide one or more return commands to the aerialvehicle.

FIG. 4 is a graphical representation 400 depicting a minimum fuel flowthreshold that can be used in accordance with example embodiments of thedisclosed technology. Fuel flow 402 is graphically depicted asincreasing from the bottom to the top, relative to the page. A currentfuel flow 410 is depicted, having a maximum fuel flow level amongst thedepicted fuel flows. A minimum fuel flow 420 threshold is depicted. Theminimum fuel flow 420 may represent a fuel flow requirement to provide alean blowout (LBO) margin for the combustor. A fuel flow at or above theminimum fuel flow 420 can be expected to provide a sufficient fuel/airratio to avoid lean blowout. A fuel flow below the minimum fuel flow420, however, can be expected to provide a fuel/air ratio that mayresult in lean blowout.

A first predicted fuel flow 430 is depicted, corresponding to apredicted fuel flow with a TCMA test function active under a first setof engine operating conditions. The first predicted fuel flowcorresponds to a predicted fuel flow during a TCMA test function. Inexample embodiments, the TCMA test function may include actuating a fuelreduction valve. As FIG. 4 depicts, the first predicted fuel flow 430with the TCMA test active is greater than the minimum fuel flow 420. Insuch a situation, the TCMA test unit may determine that the TCMA testshould be performed. Accordingly, a TCMA test command can be generatedby the TCMA test unit and provided to the TCMA system. A TCMA test canthen be executed. A TCMA test command 450 can be provided in oneembodiment.

A second predicted fuel flow 440 is depicted, corresponding to apredicted fuel flow with the TCMA test function active during a secondset of operating conditions. As FIG. 4 depicts, the second predictedfuel flow 440 is less than the minimum fuel flow 420. In this situation,the TCMA test unit may determine that the TCMA test should not beperformed. Accordingly, the TCMA test unit can generate a TCMA test skipidentifier 460. The TCMA test may can be skipped or otherwise notperformed in order to avoid lean blowout of the combustor.

FIG. 5 is a flowchart depicting a process 600 of selectively performinga thrust control system test based on a predicted fuel flow of a gasturbine engine. In example embodiments, process 600 may be performed byone or more computing devices implementing a flight management systemand/or an engine control system. For example, process 600 may beperformed by TCMA test unit 320 in some implementations. FIG. 5 depictssteps performed in a particular order for purposes of illustration anddiscussion. Those of ordinary skill in the art, using the disclosuresprovided herein, will understand that various steps of any of themethods disclosed herein can be adapted, modified, rearranged, ormodified in various ways without deviating from the scope of the presentdisclosure.

At (602), sensor data representing one or more measured engineparameters is obtained. For example, sensor data may be received fromone or more sensors at a flight management system and/or engine controlsystem. In another example, the sensor data may be obtained from adatabase or other storage location.

At (604), a current fuel flow is determined from the sensor data. Insome implementations, the fuel flow may be represented by one or more ofthe engine parameters. In other examples, the fuel flow may be derivedfrom the received engine parameters. In example embodiments, the fuelflow may be represented as a fuel flow rate or other measure of the fuelbeing supplied to the turbine engine.

At (606), a predicted fuel flow is determined based on the current fuelflow and a TCMA system test operation. For example, the current fuelflow can be used to predict a fuel flow that will result if a thrustcontrol malfunction accommodation (TCMA) function is activated. In someimplementations, the TCMA cutback function includes actuating a flowreduction device such as a flow reduction valve to reduce fuel flow tothe turbine engine.

In some implementations, one or more models are used at block 606 todetermine a predicted fuel flow rate. For example, various engine and orfuel system models may be used at block 606. In some examples, the TCMAtest unit may input the current fuel flow into the one or more modelsand receive as output one or more predicted fuel flow values.

At (608), one or more thresholds are determined for comparison againstthe predicted fuel flow. In some embodiments, a constant threshold maybe used at block 608. Accordingly block 608 may include accessing apredetermined threshold. In other examples, variable threshold can beused. For example, a variable threshold may include a plurality ofthresholds that are based on different operating conditions of theturbine engine. The minimum fuel flow to provide sufficient LBO marginmay vary based on the different operating conditions. Accordingly, avariable threshold may be used to accurately compare the predicted fuelflow and determine whether a potential blowout condition may occur. Assuch, block 608 may include determining one or more current engineparameters or other parameters to determine a current operatingcondition of the turbine engine. Based on the current operatingcondition, the appropriate threshold can be determined at block 608.

At (610), the predicted fuel flow is compared with the one or morethresholds determined at block 608. At (612), the system determineswhether the one or more thresholds are satisfied. For example, block 612may include determining whether the predicted fuel flow rate is at orabove a minimum fuel flow rate. At (614), a TCMA test command isgenerated to initiate a TCMA test at the turbine engine if the predictedfuel flow satisfies the threshold. For example, the TCMA test unit maygenerate a TCMA test command and issue the command to a TCMA system atthe engine control system of the aerial vehicle. In someimplementations, one or more signals can be generated at block 614 andcommunicated from the TCMA test unit to the engine control system inorder to actuate a flow reduction device incorporated within a TCMAsystem.

At (616), an identifier that the thrust control test was skipped can begenerated if the threshold is not satisfied. The TCMA test can beskipped in response to the predicted fuel flow not satisfying the one ormore thresholds. The predicted fuel flow may indicate that a potentialblowout may occur if the TCMA test is activated. Reducing fuel flow tothe turbine engine in accordance with the TCMA test may result in a fuelflow that is below a minimum level needed to provide sufficient leanblowout margin. An identifier can be generated and stored in order totrack a number of TCMA tests that are skipped by the system. In thismanner, a maintenance operation may be initiated if a predeterminednumber of test operations are skipped.

Although much of the present disclosure describes a fuel flow predictionprocess in order to selectively perform a thrust control test operationsuch as a TCMA test, the disclosed technology is not so limited. Forexample the disclosed process may be used to selectively perform anynumber of aerial vehicle operational tests or other operations. Forexample, a predicted fuel flow may be determined and compared against athreshold in order to determine whether to perform a test of any portionof the engine control system and/or fuel control system.

FIG. 6 depicts a block diagram of an example computing system 1000 thatcan be used to implement methods and systems according to exampleembodiments of the present disclosure. Computing system 1000 may be usedto implement a TCMA test unit 320, flight management system 20, vehiclecontrol system 16, etc. as described herein. It will be appreciated,however, that computing system 1000 is one example of a suitablecomputing system for implementing the control systems and othercomputing elements described herein.

As shown, the computing system 1000 can include one or more computingdevice(s) 1002. The one or more computing device(s) 1002 can include oneor more processor(s) 1004 and one or more memory device(s) 1006. The oneor more processor(s) 1004 can include any suitable processing device,such as a microprocessor, microcontroller, integrated circuit, logicdevice, or other suitable processing device. The one or more memorydevice(s) 1006 can include one or more computer-readable media,including, but not limited to, non-transitory computer-readable media,RAM, ROM, hard drives, flash drives, or other memory devices.

The one or more memory device(s) 1006 can store information accessibleby the one or more processor(s) 1004, including computer-readableinstructions 1008 that can be executed by the one or more processor(s)1004. The instructions 1008 can be any set of instructions that whenexecuted by the one or more processor(s) 1004, cause the one or moreprocessor(s) 1004 to perform operations. The instructions 1008 can besoftware written in any suitable programming language or can beimplemented in hardware. In some embodiments, the instructions 1008 canbe executed by the one or more processor(s) 1004 to cause the one ormore processor(s) 1004 to perform operations, such as the operations forpredicting fuel flow rates, including the generation of TCMA testcommands and test skip identifiers as described above, and/or any otheroperations or functions of the one or more computing device(s) 1002.

The memory device(s) 1006 can further store data 1010 that can beaccessed by the processors 1004. For example, the data 1010 can includesensor data such as engine parameters, model data, logic data, etc., asdescribed herein. The data 1010 can include one or more table(s),function(s), algorithm(s), model(s), equation(s), etc. according toexample embodiments of the present disclosure.

The one or more computing device(s) 1002 can also include acommunication interface 1012 used to communicate, for example, with theother components of system. The communication interface 1012 can includeany suitable components for interfacing with one or more network(s),including for example, transmitters, receivers, ports, controllers,antennas, or other suitable components.

The technology discussed herein makes reference to computer-basedsystems and actions taken by and information sent to and fromcomputer-based systems. One of ordinary skill in the art will recognizethat the inherent flexibility of computer-based systems allows for agreat variety of possible configurations, combinations, and divisions oftasks and functionality between and among components. For instance,processes discussed herein can be implemented using a single computingdevice or multiple computing devices working in combination. Databases,memory, instructions, and applications can be implemented on a singlesystem or distributed across multiple systems. Distributed componentscan operate sequentially or in parallel.

Although specific features of various embodiments may be shown in somedrawings and not in others, this is for convenience only. In accordancewith the principles of the present disclosure, any feature of a drawingmay be referenced and/or claimed in combination with any feature of anyother drawing.

This written description uses examples to disclose the claimed subjectmatter, including the best mode, and also to enable any person skilledin the art to practice the claimed subject matter, including making andusing any devices or systems and performing any incorporated methods.The patentable scope of the disclosed technology is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims if they include structural elements that do not differ from theliteral language of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

What is claimed is:
 1. A computer-implemented method of reducing combustor blowout during turbine engine testing, comprising: receiving, by a system comprising at least one processor, sensor data associated with at least one sensor for a turbine engine, the sensor data identifying a current fuel flow associated with the turbine engine; determining, by the system, a predicted fuel flow of the turbine engine based at least in part on the current fuel flow and a fuel flow reduction associated with an engine operational test; comparing, by the system, the predicted fuel flow to at least one threshold; and selectively initiating, by the system, the engine operational test based on comparing the predicted fuel flow to the at least one threshold.
 2. The computer-implemented method of claim 1, wherein: selectively initiating the engine operational test comprises selectively initiating a thrust control malfunction accommodation (TCMA) function.
 3. The computer-implemented method of claim 1, wherein: comparing the predicted fuel flow to at least one threshold comprises determining that the predicted fuel flow satisfies the at least one threshold; and selectively initiating the maintenance test comprises initiating the engine operational test in response to the protected fuel flow satisfying the at least one threshold.
 4. The computer-implemented method of claim 3, wherein: the at least one threshold includes a minimum fuel flow for a lean blowout margin; and determining that the predicted fuel flow satisfies the at least one threshold comprises determining that the predicted fuel flow is at or above the minimum fuel flow.
 5. The computer-implemented method of claim 1, wherein: selectively initiating the engine operational test comprises selectively actuating a flow reduction valve associated with a thrust control malfunction accommodation (TCMA) system of the turbine engine.
 6. The computer implemented method of claim 5, wherein: activating the reduction valve reduces a fuel flow rate associated with the turbine engine over a range of fuel metering valve positions.
 7. The computer-implemented method of claim 1, wherein: the sensor data includes a plurality of engine parameters; the current fuel flow is represented by a first engine parameter; the plurality of engine parameters comprises at least one additional engine parameter representing a fuel split ratio to two or more fuel nozzles, a fuel temperature, an engine core speed, or a high pressure compressor discharge pressure; and determining the predicted fuel flow of the turbine engine is based at least in part on the at least one additional engine parameter.
 8. The computer-implemented method of claim 7, wherein: the at least one threshold includes a plurality of thresholds corresponding to a plurality of different engine operating states; and comparing the predicted fuel flow to at least one threshold comprises comparing the predicted fuel flow to a first threshold in response to a first engine operating state and comparing the predicted fuel flow to a second threshold in response to a second engine operating state, the first threshold and the second threshold are different.
 9. A system, comprising one or more sensors configured to generate sensor data including one or more engine parameters of a turbine engine; and one or more processors configured to: determine a current fuel flow of the turbine engine; determine a predicted fuel flow of the turbine engine based on activation of a flow reduction valve of a fuel control system associated with the turbine engine; verify whether the predicted fuel flow satisfies at least one criteria associated with lean blowout of a combustor of the turbine engine; and activate the reduction valve of the fuel control system in response to the predicted fuel flow satisfying the at least one criteria.
 10. The system of claim 9, wherein the one or more processors are configured to: generate an identifier that the fuel control system was not tested in response to the predicted fuel flow not satisfying the at least one criteria.
 11. The system of claim 9, wherein: the at least one criteria includes a plurality of thresholds corresponding to a plurality of different engine parameter values; verifying whether the predicted fuel flow satisfies the at least one criteria comprises comparing the predicted fuel flow to a first threshold in response to a first engine parameter value and comparing the predicted fuel flow to a second threshold in response to a second engine parameter value.
 12. The system of claim 9, wherein: the one or more processors are configured to obtain sensor data including a plurality of engine parameters; the current fuel flow is represented by a first engine parameter; the plurality of engine parameters comprises at least one additional engine parameter representing a fuel split ratio to two or more fuel nozzles, a fuel temperature, an engine core speed, or a high pressure compressor discharge pressure; and determining the predicted fuel flow of the turbine engine is based at least in part on the at least one additional engine parameter.
 13. The system of claim 9, wherein the one or more processors are configured to: activate the reduction valve to reduce a fuel flow rate associated with the turbine engine over a range of fuel metering valve positions.
 14. The system of claim 9, further comprising: a thrust control malfunction accommodation (TCMA) system including the flow reduction valve.
 15. The system of claim 9, further comprising: one or more aerial vehicles including the one or more sensors and the one or more processors.
 16. A non-transitory computer-readable medium storing computer instructions, that when executed by one or more processors, cause the one or more processors to perform operations, the operations comprising: determining a current fuel flow rate associated with a turbine engine; inputting the current fuel flow rate into one or more models to determine a predicted fuel flow rate of the turbine engine; determining if the predicted fuel flow rate satisfies at least one threshold criterion associated with a control malfunction system of the turbine engine; and testing the control malfunction system if the predicted fuel flow rate satisfies the threshold criterion.
 17. The non-transitory computer readable medium of claim 16, wherein the operations further comprise: generating an identifier that a test of the control malfunction system was skipped if the predicted fuel flow rate does not satisfy the threshold criterion.
 18. The non-transitory computer readable medium of claim 16, wherein the at least one threshold criterion includes a minimum fuel flow for a lean blowout margin; and determining if the predicted fuel flow satisfies the at least one threshold criterion comprises determining whether the predicted fuel flow is at or above the minimum fuel flow.
 19. The non-transitory computer readable medium of claim 16, wherein: the at least one threshold criterion includes a plurality of thresholds corresponding to a plurality of different engine parameter values; and determining if the predicted fuel flow satisfies the at least one threshold criterion comprises comparing the predicted fuel flow to a first threshold in response to a first engine parameter value and comparing the predicted fuel flow to a second threshold in response to a second engine parameter value.
 20. The non-transitory computer readable medium of claim 16, wherein: the operations further comprise receiving a plurality of engine parameters; the current fuel flow is represented by a first engine parameter; the plurality of engine parameters comprises at least one additional engine parameter representing a fuel split ratio to two or more fuel nozzles, a fuel temperature, an engine core speed, or a high pressure compressor discharge pressure; and determining the predicted fuel flow rate of the turbine engine is based at least in part on the at least one additional engine parameter. 